The present invention relates to a rotary transmission leadthrough of a tire pressure control unit for transmitting pressurized fluid from a stationary portion of a motor vehicle to a rotatably supported wheel of the vehicle in order to change the pressurization of the wheel.
Tire pressure control units are used in motor vehicles, in particular in commercial vehicles such as motor trucks, field tractors or earth-moving machinery, in order to be able to adapt the tire pressure to differing ground conditionsxe2x80x94differing terrain, road, etc.xe2x80x94or also to differing loading conditions. As a function of the terrain to be traversed, it can be useful to travel off-road with a lower tire pressure than on hard pavement. Through differing tire pressure the contact area of the tire is changed. For example, in the case of soft ground, with a lower tire pressure as large a contact surface as feasible is provided so as to prevent sinking-in. By changing the contact area the flexing work of the tire can also be changed and be adapted to the particular condition such that unnecessary tire wear is avoided.
A tire pressure control unit according to the species is described in EP 0 377 561 B1. This prior known tire pressure control unit employs a rotary transmission leadthrough for transmitting a pressure meansxe2x80x94compressed air for filling the tirexe2x80x94from the stationary part of the motor vehicle to the movably supported wheel. The rotary transmission leadthrough is formed by two concentrically disposed tube segments, between which, sealed by annular seals, are disposed two chambers with respect to the wheel one next to the other in the axial direction, relative to the rotational axis of the wheel. The one tube segment is secured on the stationary flared housing of the wheel axle and represents a stator-side annular body. The other tube segment is secured on the wheel flange and represents a rotor-side annular body. This rotary transmission leadthrough, occupying a cylindrical section behind the wheel flange, consequently extends from the wheel flange to over the axle beam. The extent of the rotary transmission leadthrough in this direction is determined by the number of chambers used, via which pressure, measurement and/or filling means are to be transmitted. Each of these chambers is sealed in the axial direction by two sealing rings. In order to attain the desired sealing, each sealing ring must be in contact on the stator-side tube segment as well as on the rotor-side tube segment.
Of disadvantage in this tire pressure control unit is the installation space required in the axial direction. Therefore, this known tire pressure control unit cannot be mounted, for example, on wheels which are connected via universal couplings such as are provided with steering axlesxe2x80x94with a drive line.
In the two-chamber system described in EP 0 377 561 B1 the one chamber serves for transmitting a control means to a filling valve associated with the wheel, with which the filling valve can be opened and closed, for example pneumatically. The further chamber serves for transmitting the pressure means for filling or also for venting the tire. Apart from this two-chamber system, feed-in systems are also known in which the compressed air line is guided through the hub and bearing of the wheel. In this system, two annular bodies disposed concentrically with respect to one another are also provided wherein the one body is supported stationarily and the other body rotatably with respect to it. However, this system has the disadvantage that the compressed air line and also the chamber must be guided through the oil-filled hub and bearing. Leakages on the rotary transmission leadthrough lead to the fact that air penetrates into the oil and thus the lubrication and cooling effect of the oil can be impaired to the point that this can lead to the destruction of the hub and bearing.
Both of the systems described have in common that in them contact seals are used, which, in particular in the case of motor vehicles not moved for a relatively long time period, such as for example military vehicles, adhesion of the seal with the adjoining annular body can occur. When the motor vehicle is subsequently moved, this annular seal is torn from the annular body. Even if this does not lead to a destruction of the sealing ring, the sealing effect is at least considerably impaired. This adhesion is also referred to as slip-stick effect.
The invention is therefore based on the task of further developing a tire pressure control unit according to the species such that with it the [sealing] tightness of the tire pressure control unit is improved and the tire pressure control unit is also suitable for installation in such motor vehicles in which only a small installation space is available in the axial direction of the wheel.
The invention is therefore based on the task of further developing a tire pressure control unit according to the species such that with it the sealing tightness of the tire pressure control unit is improved and the tire pressure control unit is also suitable for installation in such motor vehicles in which only a small installation space is available in the axial direction of the wheel.
This task is solved according to the invention thereby that
the stator-side annular body and the rotor-side annular body in the axial direction relative to the rotational axis of the wheel are disposed such that they are adjacent to one another, leaving a motion gap,
into the face, directed toward the rotor-side annular body, of the stator-side annular body for the radial sealing of the at least one chamber two concentric annular grooves are introduced,
the annular grooves with their termination facing away from the rotor-side annular body are connected to a control line which can be activated by a pressure means,
into the annular grooves are each placed one of the sealing rings, which upon pressurization is moved in the direction toward the rotor-side annular body, and
from the rotor-side annular body into the at least one chamber terminates an output line.
The tire pressure control unit according to the invention provides that the two annular bodies are disposed in an axial and not, as is the case in the known prior art, in a concentric disposition with respect to one another. The number of the width of the chambers employed, therefore, does not add to the volume in the axial direction but rather does add in the radial direction, thus in a direction in which in any case sufficient structural space is available. The rotary transmission leadthrough of the tire pressure control unit according to the invention can be secured on the wheel flange on virtually any wheel or also on the brake drum even if, for example, a universal coupling is provided in the drive line immediately adjacent to the wheel flange.
The expanse of a chamber formed by the two annular bodies extends in the radial direction toward the rotational axis of the wheel and is delimited by the two sealing rings and sealed in this direction. In contrast to prior known tire pressure control units with a concentric disposition of the two annular bodies with respect to one another and the use, absolutely required thereby, of contact seals, the subject matter of the invention provides sealing the chamber with the sealing rings only if the tire pressure is, in fact, to be controlled. Otherwise a sealing should not take place and is also not required. For this purpose, into the stator-side annular body two concentrically disposed annular grooves (groove) are introduced, into each of which a sealing ring is placed. The back end of each groove is connected to a control line such that the grooves can be pressurized. Pressurization subsequently results in a movement of the inserted sealing rings toward the rotor-side annular body until the seals contact the rotor-side annular body. In this position of the sealing rings the chamber delimited by the sealing rings is sealed. After completion of the aeration or deaeration process of the tire, the grooves are again brought into their pressureless state, such that the sealing rings, due to the natural imbalance of the two annular bodies with respect to one another, are again slightly pressed into the grooves. This sealing measure leads only to a very slight seal wear since an actual contact and wear contact is only given at those points in time at which tire aeration or tire deaeration takes place. Moreover, the sealing rings can have a specific material rating such that replacement of the sealing rings can be adapted to specific maintenance cycles of the motor vehicle.
From the rotor-side annular body terminates an output line, for example a bore, in the chamber such that a pressure means introduced into the chamber can be supplied to the tire via this output line.
The chamber of the rotary transmission leadthrough for transmitting the pressure means can be formed alone thereby that the radial delimitation takes place by the sealing rings. However, if it is provided that between the two annular bodies only a narrow motion gap is left, it can be provided to introduce into one of the two or also into both facing components of the chamber delimitation, given by the annular bodies, a groove enlarging the cross section of the chamber.
The tire pressure control unit according to the invention is suitable for operating an introduction system as well as also for operating a two- or multiline system. In a two- or multiline system each chamber is delimited by two seals in the described manner. It can therein be provided that two adjacent grooves are separated from one another by a single common seal.
A useful implementation provides disposing in a sealing groove, in addition to a first sealing ring set thereinto through the pressurization, a further sealing ring which serves for contacting the rotor-side annular element. The properties of the first sealing ring serve for sealing the groove. The further sealing ring has an especially high abrasion and thermal resistance, such that through the properties wear of the seals during their contacting of the rotor-side annular body is reduced.
Further advantages and developments of the invention are described in the following description of an embodiment example of the invention with reference to the enclosed Figures.